Studies of fire debris from bomb blasts using ion chromatography, gas chromatography–mass spectrometry and fluorescence measurements – evidence of ammonium nitrate, wax-based explosives and identification of a biomarker

Abstract

Investigative analysis of fire debris residues from bomb blasts in Midnapore, West Bengal was carried out. The explosives were found to be ammonium-nitrate based, as shown from the preliminary analysis of water soluble residues and ion-chromatographic experiments. The characteristic features of the explosives, i.e. the absence of fuel oils and presence of the waxes, were confirmed from gas chromatography-mass spectrometric measurements of the acetone-soluble and ether-soluble extracts of the explosive residues. The presence of wax was also confirmed from fluorescence measurements of the ethereal extracts and comparative studies of TICs of gas chromatography-mass spectrometry of normal waxes and wax in the ethereal extracts of the experimental samples. But the most important aspect of the study was the presence and identification of a biomarker 28-Nor-17.beta.(H)-hopane both in normal wax samples and fire debris residues. The results conclusively showed the ordinary wax to be the fuel, and the source of the fuel was the same in all cases. Mass spectra of 28-Nor-17.beta.(H)-hopane was confirmed by library matching. All the ingredients of the explosives (inorganic ingredients, wax and a single biomarker) pointed to the fact that the explosions were carried out by a particular group.

Keywords:

• ammonium nitrate
• biomarker
• fluorescence
• gas chromatography–mass spectrometry
• improvised explosive device
• wax